The present invention relates to an apparatus for desalination and purification of water by reverse osmosis and ultrafiltration, which apparatus comprises: plate-like carrier plates and water-guiding plates which are stacked alternately one upon the other and are secured between two end plates; ring-shaped diaphragms which are disposed between the carrier plates and the water-guiding plates and are lined with a filter sheet, with untreated water flowing over the diaphragm side of a given diaphragm, and permeate being withdrawn from the filter side thereof; and sealing arrangements disposed at the periphery of each water-guiding plate between untreated-water passages and permeate-withdrawal passages; beyond the edges of the guide plates, the carrier plates rest upon one another via a widened edge portion, and form, via a gap produced by a reduced thickness of the edge portions of the carrier plates, a permeate-withdrawal passage which communicates with the filter sheets of the diaphragms.
Apparatus of the aforementioned type, as they are disclosed, for example, in the U.S. Pat. No. 4,228,014, which belongs to the Assignee of the present application, must be serviced at regular intervals; in other words, the apparatus must from time to time be provided with new diaphragms, or at least the diaphragms must be freed of deposits, such as algae, sewage, and the like. Since such servicing always involves (at least partial) interruption of operation, it is essential that the apparatus for desalination and purification of water not only be capable of being rapidly disassembled, but also be capable of again being very rapidly reassembled without any alignment and sealing errors. Up to now, this reinstallation has been extremely time consuming and involved a lot of work, since the seals which were used were always multi-part and also were made of different materials. U-shaped edge seals for the water-guiding plates had to be laboriously placed on the toothed rim of the water-guiding plates, and holding rings or water-guiding rings also had to be inserted, on the one hand to hold the annular diaphragms and filter sheets in position, and on the other hand to also support the carrier plate seals on the periphery, so that the latter cannot shift out of position when the untreated-water stream is redirected in the region of the edges of the guide plates.
It is therefore an object of the present invention to provide for apparatus of the initially mentioned type an improved peripheral seal which permits assembly of a modular stack to be carried out considerably more easily and rapidly.